The present disclosure relates to a piezoelectric element driving apparatus and method allowing for high output while protecting dielectric characteristics of the piezoelectric element using an asymmetrical driving signal, and a piezoelectric system using the same.
In accordance with an increase in interest in user interfaces and the development of user interface-related technology, a user data input reaction technology has become an importable element in user interfaces in terminals.
Initial reaction technology has been used to provide simple vibrations in response to user data input to allow a user to confirm data input.
Recently, as it has been important to provide more precise reactions or vibrations to user data inputs. In order to address this issue, a technical transition from touch reaction technology, according to the related art, based on motor driving technology, to haptic technology capable of providing various reaction elements has been made.
Haptic technology generally indicates an overall system transferring tactile sensations to a user. In haptic technology, a predetermined vibration element may be vibrated to transfer physical impulses to a user, thereby providing the user with tactile sensations. Recently, it the provision of various reactions in order to provide user feedback, based on greater precision in controlling has been demanded.
In such haptic technology, the provision of various vibration patterns using various frequencies has been demanded. In order to satisfy this demand, a piezoelectric actuator formed of ceramic has been used in recent times. Such a piezoelectric actuator has a faster response speed, a reduced amount of noise, and a higher resonance bandwidth as compared with existing linear resonance actuators or existing vibration motors containing magnets.
An initial piezoelectric actuator is formed of a single piezoelectric layer, such that it requires a voltage exceeding 100V as a driving voltage for the driving thereof. Therefore, in a mobile terminal such as a smartphone, significant amounts of power are consumed due to the driving of the piezoelectric actuator formed of the single piezoelectric layer.
In order to solve this problem, a piezoelectric element formed of a plurality of piezoelectric layers has been used. However, a piezoelectric element formed of the plurality of piezoelectric layers has a limited range of driving voltages.
Particularly, in the case in which a driving voltage of a negative electrode, among such driving voltages, is strongly applied, the disposition of electrical charges in dielectric portions of the piezoelectric element is affected, such that piezoelectric characteristics of the dielectric are lost. Therefore, a piezoelectric element formed of the plurality of piezoelectric layers has a very limited operating voltage. In addition, due to the limitation of the operating voltage, output characteristics of the piezoelectric element may be reduced.